This project proposes to examine the orientation and organizational structure of two phage T4-coded integral membrane proteins and their interaction with the deoxyribonucleotide synthetase complex. These proteins are coded by the DNA-delay genes, 39 and 52. Mutations of these genes decrease not only DNA replication but also deoxyribonucleotide synthesis. We are studying the nature of the interaction of the DNA-delay proteins with the membrane, and with the synthetase complex. We have purified T4 ribonucleoside diphosphate reductase and the T4 DNA topoisomerase as a part of these studies.